Glycyrrhetinic acid esters and the method of preparation thereof



Oct. 8, 1968 TAKEQ UEDA I 3,405,152

GLYCYRRHETINIC ACID ESTERS AND THE METHOD OF PREPARATION THEREOF FiledMay 10, 1965 5 Sheets-Sheet 1 Fig 0: OOOOO O. q-mrONNc\|--.

WA\ /ENUMBER mm") LLI WAVENUMBER (Cm' Oct. 8, 1968 TAKEO UEDAGLYCYRRHETINIC ACID ESTERS AND THE METHOD OF PREPARATION THEREOF 3Sheets-Sheet 2 Filed May 10, 1965 WAVENUMBER .(Cm"') -oow 89 0o -ooE com-091 8m oom. so o8 com 88 00mm 00mm Oowm -Oowm WAVENUMBER 1cm") Oct. 8,1968' TAKEO UEDA GLYCYRRHETINIC ACID ESTERS AND THE METHOD OFPREPARATION THEREOF 5 Sheets-Sheet 5 Filed May 10, 1965 0 -89 -oo og -82-83 -89 699. -oot -89 -82 88 8% -ooww -oomm 68m WAVENUMBER ((Zm") UnitedStates Patent fice 3,405,152 Patented Oct. 8, 1968 ABSTRACT OF THEDISCLOSURE Novel glycyrrhetinic acid esters represented by the formula:

wherein R is selected from the class consisting of stearyl and oleylgroups, and R is selected from the class consisting of hydrogen,stearoyl and oleoyl groups.

This invention relates to novel glycyrrhetinic acid esters and themethods of preparing thereof.

These compounds have a generic Formula I such as follows:

(I) COOR (11) H30 oooH in which two foregoing formulas R" is an alkanoylgroup of not more than 4 carbon atoms and R' is an alkyl group of notmore than 4 carbon atoms in their respective formulas.

The anti-inflammatory effect of these compounds however is only equalto, if not less than, that of glycyrrhetinic acid.

I found that the glycyrrhetinic acid esters of the present invention notonly had an anti-inflammatory effect much superior to that ofglycyrrhetinic acid, but also that it excelled in its solubility in fatsas well as its solubility in organic solvents.

Thus, the product of this invention is suitable fo use in oilpreparations, salves, emulsions and sticklike preparations and exhibitsan excellent anti-phlogistic effect because of its good transcutaneousabsorption. This is a characteristic which was not noted in the knownglycyrrhetinic acid and its esters and is an unexpected result.

Further, it was found that the invention product could be used for thesame purpose as the corticoidal hormones. And in this case, a noteworthycharacteristic of the invention product is the fact that side reactionssuch as were manifested in case of the corticoidal hormones, i.e.,deposits of sugar and shrinkage of the adrenals, do not occur. In otherwords, the invention product has excellent uses as an anti-phlogisticagent because of its very low toxicity and absence of side reactions.

These compounds (I) of the present invention are prepared by reacting anesterification agent with a compound having the following Formula IV:

(IV) C O OH wherein R has the meaning hereinbefore defined.

For example, these compounds (I) are prepared by reacting stearyl oroleyl halide with the compound (IV) in the presence of an alkalinecatalyst such as an alkali bicarbonate, alkali carbonate, organic aminesor other alkaline substances.

Further, the compounds (I) can also be obtained by reacting stearyl oroleyl alcohol with the compound (IV) in the presence of an acidesterification accelerator such as hydrochloric acid, sulfuric acid andaromatic sulfonic acids.

Further, a compound such as of the following Formula VI (this compoundis comprehended by the compound having the aforsaid Formula I) can alsobe prepared by 3 reacting a glycyrrhetinic acid ester having thefollowing Formula V with stearyl or oleyl halide.

in which two foregoing formulas R has the meaning as hereinbeforedefined and R"" is selected from the class consisting of stearoyl andoleoyl groups.

The accompanying drawings are in all cases infrared spectrum curves,FIGS. 1-4 being those of the invention compounds obtained in Examples1-4, respectively, whereas FIG. is that of glycyrrhetinic acid presentedas a control.

The following examples are given to illustrate the invention further, itbeing understood however that these examples are not in limitation ofthe invention.

EXAMPLE 1 Preparation of stearyl glycyrrhetinate A mixture of 2.35 g. ofglycyrrehetinic acid, 1.67 g. of stearyl bromide and 0.5 g. of potassiumbicarbonate is heated under reflux for hours in 30 cc. of anhydrousethanol. After completion of the reaction, the reaction mixture isfiltered and concentrated. Then when the crystals deposited aftercooling are recrystallized from anhydrous ethanol, 2.88 g. of colorless,flaky crystals having a melting point of 116-1 18 C. are obtained. Theinfrared absorption spectrum curve of these crystals are as shown inFIG. 1, and the elementary analysis results and calculated values (as CH O are as follows.

Calculated values: C:79.72%, H=11.43%. Experimental values: C=79.58%,H=11.25%.

EXAMPLE 2 Preparation of stearyl glycyrrhetinate Thirty cc. ofchloroform are added to 30 g. of stearyl alcohol and dissolved. In thissolution are suspended 4.7 g. of glycyrrhetinic acid, followed bypassing anhydrous hydrochloric acid gas therethrough for 4 hours. Afterallowing to stand overnight, the mixture is heated on a water bath andthe hydrochloric acid gas and chloroform are distilled off. This isfollowed by distilling off of the excess stearyl alcohol on an oil bathat reduced pressure. When the residual product is recrystallized fromethanol, 2.6 g. of colorless, flaky crystals having a melting point ofll61l8 C. are obtained.

The infrared absorption spectrum curve of these crystals are as shown inFIG. 2.

4 EXAMPLE 3 Preparation of oleyl glycyrrhetinate 4.7 g. ofglycyrrhetinic acid are suspended in 20 cc. of oleyl alcohol, followingwhich anhydrous hydrochloric acid gas is passed therethrough for 2hours. After allowing this suspension to stand overnight, it is heatedon a water bath, followed by reducing the pressure to eliminate thehydrochloric acid gas. This is followed by heating over an oil bath atreduced pressure to distill off the excess oleyl alcohol to therebyobtain a jelly-like residual product. This product is, dissolved inbenzene and, after purifying by passing through a column of alumina, thebenzene is distilled off completely. The yield is 6.1 g.

The infrared absorption spectrum curve of this product is as shown inFIG. 3 and the results of an elementary analysis and calculated valuesare as follows.

Calculated values: C=79.29%, H=11.09%. Experimental values: C=79.64%,H=10.88%.

EXAMPLE 4 Preparation of stearyl-stearoyloxyglycyrrhetinate 1.48 g. of3-stearoyloxyglycyrrhetinic acid are dissolved in 20 cc. of anhydrousethanol, following which 0.67 g. of stearyl bromide and 0.15 g. ofanhydrous sodium carbonate are added. The mixture is then refluxed for 5hours on a water bath. After completion of the reaction, the reactionmixture is filtered While hot and the filtrate is concentrated followedby addition of a small amount of water. The crystals deposited aftercooling are separated by filtration. When these crystals arerecrystallized from ethanol, 1.64 g. of colorless crystals are obtained.

The infrared absorption spectrum curve of these crystals is as shown inFIG. 4, and the results of an elementary analysis and calculated values(as C H O are as follows.

Calculated values: C=79.94%, H=1l.99%. Experimental values: C=79.77%,H=1l.86%.

EXAMPLE 5 This example illustrates the pharmacological test of theinvention chemical substances.

The materials of the experiment The following compounds were used in theexperiment.

( 1) Stearyl glycyrrhetinate (a compound of Formula I wherein the R andR therein are a stearyl group and hydrogen, respectively).

(2) Oleyl glycyrrhetinate (a compound of Formula I wherein the R and Rtherein are an oleyl group and hydrogen, respectively).

(3) Stearyl 3-stearoyloxyglycyrrhetinate (a compound of Formula Iwherein the R and R therein are stearyl group and a stearoyl group,respectively).

(4) 3-acetoxyglycyrrhetinic acid.

(5) 3-lauroyloxyglycyrrhetinic acid.

(6) 3-palmitoyloxyglycyrrhetinic acid.

(7) Lauryl glycyrrhetinate.

(8) Cetyl glycyrrhetinate.

The procedures of the experiment Male rats of the Wistar weighing about150 grams are administered by the hypodermic injection of glycyrrhetinicacid and the derivatives thereof daily for 7 successive days. The doseadministered is millimole/Z mL/kg. as a 1% Tween sesame oil suspension.

The anti-inflammatory effect was tested by means of animal experimentsusing the following procedures.

(1) Rat foot test [H. Selye, Brit. Med. Jour. 2, 1129 (1949)]: The testdrug is injected hypodermically into rats daily 'for 7 days. On the lastday, 0.1 ml. of

from Table II, the following compounds have the belowindicated rates.

solution of physiological saline in formalin is injected Percent intothe tendinous membrane of the sole of the back feet Stearylglycynrhetinate 40.1 of the rats. The extent of the increase in theswelling of 5 Oleyl glycyrrhetinate 35.1 the feet after the lapse of 1,2, and 3 hours are measured Stearyl 3-stearoyloxyglycyrrhetinate 43.2and the difference in the average value of the increase when these arecompared with the inhibition rate of the Swenmg P P 1 feet between f FFf and glycyrrhetinic acid, letting 1.00 be the rate of the latter,treated rats are indicated as the rate of inhibition. h follo i ratiosare b i d (2) The cotton pellet method [R. Meier et al., Experi- 10Times mented, 6, 469' (1959)]: Four dental cotton pellets of s l l h ti2,78 about 5 mg. are weighed and then each is transplanted to Oleylglycyrrhetinate 2.44 the axillae and inguinal regions of a rat,following which Stearyl 3-stearoyloxyglycyrrhetinate 3.00

TABLE I Swelling of Foot Inhibition N 0. Drugs rate, per- InhibitionIncrease Difference cent ratio of increase 1 Control 27510.21 2..Glyeyrrhetinie acid 2 3010.19 0.451003 16.3 1.00 3.-

3-aeetoxyglyeyrrhetinie aeid 2 4210. 03310.02 12.0 0.73 4..3-lauroyloxygiyeyrrhetinic acid... 2 7210.17 0.0310. 01 1. 1 0.07 5..3-pahnitoyloxyglyeyn'hetinio acid 2 6210.22 0.151001 5.5 0.34 6 22010.16 0. 5510.03 20.0 1.22 7 2 1010.16 06510.04 23.6 1.44 8 17210.12 1. 0310. 09 37.5 2.30 9.. Oleyl glycyrrhetinate 1 7410.141.0110. 09 36.7 2. 10 Stearyl 3-stearoyloxyglycyrrhetinate 1 5410.10 1.2110. 10 44.0 2. 69

TABLE II Weight of Cotton Pellet N0. Drugs Inhibition InhibitionIncrease Difference rate, perratio of increase cent Control 8. 9510. 72Glyeyrrhetinic acid 7 6610. 71 1. 2910. 08 14.4 1.003-aeetoxyglyeyrrhetinie aeid.... 8 1210.70 0 8310.06 9.2 0. 64 31anroyloxyglycyrrhetime aeid.... 8 5210.68 0 4310.03 4.7 0.333-palmitoyloxyglyeyrrhetinic acid.. 8.4710. 74 0 4810. 03 5.3 0.37Lauryl glycyrrhetinate....' 7. 2610. 49 1 691011 18.8 1.31 Cetylglyeyrrhetinate. 7. 1010. 53 1 8510. 0Q 20. 6 1. 43 Stearylglycyrrhetinate. 5. 3610. 28 3 5910. 29 40. 1 2. 78 Oleylglyeyrrhetinate- 5.8010. 36 3. 1510. 21 35. 1 2. 44 Stearyl3stearoyloxyglycyrrhetinate 5. 0810. 41 3. 8710. 31 43. 2 3. 00

Results of the experiments The results obtained in the rat foot andcotton pellet tests are shown in Tables I and II, respectively.

When the anti-inflammatory effect of the several compounds, as obtainedby the rat foot test, is indicated by means of the inhibition rate, asis apparent from Table I, the following compounds have the rates asindicated below:

Percent Stearyl glycyrrhetinate 37.5 Oleyl glycyrrhetinate 36.7 Stearyl3-stea-royloxyglycyrrhetin-ate 44 When these are compared with theinhibition rate of glycyrrhetinic acid, letting 1.00 be the rate of thelatter, the following ratios are obtained.

Times Stearyl glycyrrhetinate 2.3 Oleyl glycyrrhetinate 2.25 Stearyl3-stearoyloxyglycyrrhetinate 2.69

Next, when the anti-inflammatory effect of the several compounds, asobtained by the cotton pellet test, is indicated by means of theinhibition rate, as is apparent As described above, the results of therat foot test and the cotton pellet test show a similar tendency, itbeing shown that stearyl glycynrhetinate, oleyl glycyrrhetinate andstearyl 3-stearoyloxyglycyrrhetinate of the present invention, in allcases, have a much more potent antiinflammatory effect than thereference compound glycyrrhetinic acid. The other compounds manifestedresults which were only equal to, if not less, than glycyrrhetinic acid.Hence, it can be said that the compounds of the presentinvention arenovel anti-inflammatory agents whose effect is much more potent than theknown glycyrrhetinic acid.

I claim:

1. A glycyrrhetinic acid ester represented by the generic formulawherein R is selected from the class consisting of stearyl and oleylgroups, and R is selected from the class consisting of hydrogen,stearoyl and oleoyl groups.

7 s 2. Stearyl glycyrrhetinate having the formula 4. Stearyl3-stearoy1oxyglycy1=rhetinate having the H30 0 0001 11,, formula 0=/\CH3 i CH3 0- CH3 011i cm 10 I i 110- V 3 UnllaaCO-O HaC on; x 3. Oleylglycyrrhetinate having the formula 5 1130 OH;

H C 0000 H 3 ls N References Cited FOREIGN PATENTS 20 894,265 4/1962Great Britain.

0- OTHER REFERENCES C11; Brewster: Organic Chemistry (1948), pp. 218-20.

EV 25 HENRY R. JILES, Primary Exam e H10 on:

